Contribution Title: Smart Environment and Energy

In this chapter, we discuss the traditional resources and energy recovery process as well as the smart resources and energy recovery process. Our concentration is the treatment of digestion liquid after anaerobic fermentation. Because digestion liquid has huge environmental hazards and resource potential. We describe the technique of recovering struvite from anaerobic digestion liquid using smart constant voltage electrolytic crystallisation method as an example of recovering nitrogen and phosphorus from wastewater. We designed a smart magnesium anode constant voltage electrolytic crystallisation device to achieve smart and automated resources and energy recovery by controlling the power supply and struvite recovery. We compared the treatment efficiency of the device under different voltage, initial pH, and wastewater quality conditions. We revealed that the recovery efficiency of phosphorus was maintained at a relatively high level in the voltage range of 2 V–12 V. And the recovery of nitrogen and phosphorus was effective in the initial pH range of 3–8. Furthermore, we have built a smart constant voltage electrolytic crystallisation device with solar light panels as the power source under 2 V voltage conditions. It has a perfect application potential for eutrophic water bodies. The device not only has a high recovery rate for struvite, but also has a high potential for vivianite and heavy metal recovery. In the age of rapid development of smart resources and energy technology, it is expected to become a new generation of large-scale application technology.